Hi Chandan, the standalone is the already compiled working/running package released with support from the openmrs developers to the whole openmrs community whereas what we have on github is the code behind what you see in the standalone,
The standalone can have be missing some features when compared with the build from the code since we keep on contributing to the code, and the code is organized in branches on github, the master branch is the one that is in most cases the one with the yet to be released branch, though in this case 1.10.x will be first released, a release is a standalone version of openmrs,
Something else is that you too can set up master or 1.10.x or 1.9.x(specially) to run as reference application(2.0).
Previously we have released 2.0 as the first release build on the UIFramework, it has so many changes compared to the previous legacy applications. i refer you to some pages here.
openmrs.org/2014/02/introducing-openmrs-2-0https://wiki.openmrs.org/display/docs/Step+by+Step+Installation+for+Developers
https://wiki.openmrs.org/display/docs/Reference+Application+dev+environment+setup